This invention relates to an apparatus for interfacing a plurality of signals to a processor, and more particularly, to an interface apparatus for interfacing a selectable plurality of different types of signals to a process control system.
In present day process control systems, interface devices are utilized to couple predetermined types of signals to the process control system, the predetermined types of signals being high-level analog, low-level analog, digital, . . . . Because of a rigid structure of these present day interface devices, only predetermined types of signals are permitted to be coupled to these present day interface devices. Also, the rigid structure provides only a predetermined number of control loops and secondly, only a predetermined number of input/output (I/O) for the control loops. Because some control tasks are more control processing intensive than others, and some tasks are more I/O intensive than others, it is desirable to interface selective tasks to the process control system via the interface device which will insure effective and efficient completion of these tasks, i.e. control processing and I/O. However, the configuration provided by the structure of these present day interface devices is essentially fixed, i.e., restricting what the user can do to efficiently tailor the configuration to specific user requirements, thereby limiting the number and types of tasks which can be coupled to the interface device.
The interface apparatus of the present invention permits a flexible quantity of different types of I/O signals to be interfaced (to the process control system) via the interface apparatus due to the architecture of the interface apparatus which essentially separates the processing of control from the I/O of control, thereby permitting the user to configure the system to meet a defined control strategy, without the limitations imposed by previous systems. Further, the processing of control can be eliminated altogether in the interface apparatus of the present invention. In this case the processing of control is performed by a controller external to the interface apparatus, thus permitting the interface apparatus to function as a data aquisition unit, thereby adding to the configuration flexibility.